My sister has always eaten toilet paper. Now she complains of stomach aches. What would a doctor do to her?

Rule out bezoar. Stomach-aches have many causes, but there have been numerous reports of ingested toilet paper causing obstruction, as a "bezoar" in the stomach, or in the colon. She'll get examined, maybe endoscoped or imaged, and if it's the toilet paper, treatment will save her life. This is a poor way of dieting, or a compulsive "pica"; in either case a clever physician can help guide her as well.
Refer. Your sister suffers from a very serious physical and mental behavior problem. Need to see doctor immediately, for referral to psychiatrist for serious psycholoical therapy. She is ingesting bleach, chlorine and hundreds of cancer causing chemical agents that seriously puts her life at risk. May need to take iron supplements, too. Please have her checked out.